not too low) so can be used to make a large number of jellies.
Gels made with agar agar have the disadvantage that the gel formed is easily broken and not as
elastic as gelatine – however elasticity can be improved by the addition of sorbitol or glycerol (more
commonly named glycerine) to the gel base, although these products are associated with laxative
Because the preparation needs to be boiled to dissolve the agar agar, it is not useful for gels that are
to be mad from “raw” liquids (such as fresh parsley, oysters, gazpacho, etc.) – however, this problem
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can to extent be overcome by just dissolving the desired amount of agar agar in a very small quantity
of boiling liquid, and adding this to the large amount of raw liquid, to keep the “fresh” taste, however,
the gel will form very quickly and is difficult to handle.
Alginate is a gelling agent extracted from brown algae. It is composed of long strands composed of the
two basic subunits – gluronic acid and mannuronic acid:
How it works
When alginate is added to a liquid, it will act as a thickener. In the presence of calcium ions, a mixture
containing alginate will form a gel. The calcium ions insert themselves between individual alginate
strands and will allow them to interlock and form a gel, in an arrangement similar to an egg box.
Alginate strands (zig zag lines) forming a network around the Ca ions present (circles)
The ability of a certain alginate to thicken or gel will depend on its relative proportions of gluronic and
manuronic acid (for example, alginates high in gluronic acid will be more effective gelling agents).
Because alginate forms gels uniquely in the presence of calcium, the food industry used it to make
“fake caviar”: drops of an alginate containing solution are slowly pipetted into a large bowl of water
containing a high concentration of calcium ions – the outside of the drop, which is in contact with the
calcium, will instantly form a gel, while the centre of the bead, which is not in contact with the calcium